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Habitat loss and fragmentation, and plant genetic conservation
Massive land use changes have taken place in the 20th century. Extensive areas of wildflower meadows, fens and wetlands in river valleys have been drained and converted for intensive agricultural use. Many semi-natural ancient woodlands have been destroyed and converted to agriculture or intensive forestry. New factories, housing estates and airports have also eaten away wildlife habitats such as heath, wetland and species-rich grassland. The result, especially in the lowlands, has been that native plant communities associated with our most valued wildlife habitats are now largely confined to isolated pockets.
Native plants associated with these habitats have evolved over thousands of years. They may be adapted to the local climate, perhaps also to specific soil characteristics and the management associated with specific sites.
The genetic blueprint held by these isolated plant populations is still at risk from habitat change, but an additional and quite unknown risk is associated with the practice of ecological restoration. This involves the large-scale re-introduction of native plants into areas of the countryside (and towns) which have become wildlife-poor in recent decades. The creation of new native woodlands and reseeding of former arable land with native wildflowers are two examples.
Are isolated and fragmented populations at risk from these large-scale plant reintroductions? Or can ecological restoration be managed in a way to minimise any risks and provide maximum benefits for the wildlife which depends upon native plant communities?
Flora locale's work aims to promote good practice in ecological restoration. The present scarcity of knowledge on native plant genetics leads us to promote the precautionary principle, and the guidance found in our Technical notes is based on this approach.
Plant introductions
Flora locale was established in 1997 as a response to increasing concern over large scale introductions of native plants of distant, selected or cultivated origin. These "introductions" are:
- Selectively bred "Distinct, Uniform and Stable" agricultural varieties (many common grasses, vetches, trefoils and other species for which it is prohibited to sell wild varieties under EC law)
- Trees that have been sourced from "Selected" stands chosen to serve the timber trade and which often lack the genetic diversity and characteristics represented in the wild
- Seed and plants that originate from wild plant communities in other countries ñ these may be adapted to different climates and other conditions, and may be forms or varieties not found in the UK.
In recent years there has also been increasing concern over:
- translocating native plants from one part of a country to another, especially if it is a species which is local or uncommon, and where locally adapted populations may be at risk of being swamped by non-local ones
- introducing native species into areas where they had never before occurred (i.e. outside their natural distributional range)
- the introduction of genetically modified native plants, and close relatives of native plants, in horticulture, forestry and agriculture
- the introduction of other artificially modified native plants developed through traditional selective plant breeding techniques.
Consequences for biodiversity of such introductions are largely unknown, due to little research having been done on this important issue, but potential consequences are:
- erosion of existing genetic diversity represented among populations of related native plants
- missed opportunities to restore fragmented populations of locally adapted forms of native plants
- imposition of potentially adverse changes to ancient and historically important wildlife areas, such as ancient semi-natural woodlands and hedgerows that have been relatively unaltered by planting in recent centuries
- potential consequences for associated fauna (for example, some bumblebees are unable to feed from certain Red Clover (Trifolium pratense) cultivars because the flower is a different shape from native forms)
- in some circumstances, introduced material may survive poorly because it is not well adapted to the site or locality ñ prejudicing the success of an ecological restoration project.
The introduction of non-native ("alien") species is also a major problem throughout the world. In the UK the greatest problems from introduced and invasive species are associated with aquatic plant introductions but many alien species are associated with imports of grass, wildflower and crop seed . Species such as New Zealand Swamp Stonecrop (Crassula helmsii) and Floating Pennywort (Hydrocotyle ranunculoides) currently threaten nationally and internationally important wildplant communities in England. Although "alien species" is not currently a major workstream of Flora locale, landscape and ecological restoration projects provide one vehicle for introducing alien plants, pathogenic fungi and other fauna into Britain. A greater emphasis on sourcing native plants from indigenous sources would to some extent reduce the risk of introducing additional alien species.
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Lack of information on plant origin
For the people who buy or use native plants for large-scale landscaping, forestry or ecological restoration projects, the lack of information on the native origin of plants they buy has been a significant problem. Currently, the majority of plants and seed on sale do not say where they originate from. There is also a different interpretation of terms, such as "origin" and "provenance" used in horticulture. This creates confusion, and makes selection of plants of appropriate origin almost impossible.
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Restrictive EC Legislation
UPDATE: Legislation has recently been changed, to enable the legitimate trading of wild seed mixes containing fodder species, and source-identified trees. Links to relevant documentation are available via the Suppliers page or the Online Library (search on "regulation" and "FRM" or "reproductive"). The following was the situation until 2000 (trees) and 2005 (fodder seed/preservation mixtures). Two European laws currently prohibit the sale and marketing of genetically diverse wild plant seed of certain species and certain timber trees. Only registered "Distinct, Uniform and Stable" seed of many grasses, vetches, clovers, trefoils and other fodder plants can be sold. Timber trees, such as Oak and Beech must only be marketed if the are sourced from "Selected" stands that have been chosen for their timber producing quality. A recent example provided to us from a Kent nursery highlights the issue ñ the nursery was not allowed to collect oak seed from local woods because the trees were "too small", and so had to collect seed from French woods instead (which were then grown into trees planted in Kent and other British woods).
This situation has now changed, and the Forestry Commission has developed a voluntary scheme for native trees and shrubs. However, the UK countryside now holds a legacy of inappropriate planting that has taken place over the last 40 years, where the majority of trees and shrubs that have been planted are not of UK native origin, and practically all of timber trees have originated from a limited number of Selected stands.
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"Fix it quick"
Pressure is often on those responsible for projects to plant sites up quickly. There is an inadequate supply of appropriate native planting material to satisfy the volatile demand, so the result is that much of plants and seed that are used are from introduced or cultivated sources. The fix-it-quick approach is happily, no longer supported by national and local government funding policies. However, tight budgets and the need to spend within the financial year require planting grants to be spent, or landscape contracts to be completed, within a short time period. This puts pressure on contractors to find the cheapest sources of planting stock and less care may be taken in procuring appropriate planting stock.
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Substitution
Substitution is a common practice in the horticultural trade. It is the act of supplying a different species or variety to that ordered, when the original is unobtainable. Due to small print in their terms of supply that says they have the perogative to supply something different if the stock that is ordered is not available it can rarely be successfully challenged. This practice allows nurseries and seed houses to supply material of introduced origin when this is not desired by the plant user.
One supporter of Flora locale had problems with Wild Daffodils (Narcissus pseudonarcissus) which were ordered to plant under a new woodland. When the plants flowered in spring the landowner was surprised to see they were a widely available cultivated form. She had to dig them up and wait another year before obtaining the bulbs she had actually ordered.
Other common complaints is that British native origin stock was wanted but customers are supplied with continental-origin stock. This has been a frequent occurrence for hedging material during the 1980s and 1990s as nurseries that have bought in young stock have bought faster-growing Italian or Hungarian stock. This comes into leaf up to three weeks earlier than British native counterparts. Much of the hedging planted on farms and along highways during this time has not originated from British origin stock and threatens the integrity of phenology reporting (timing of bud burst and flowering used to consider climate change impacts on wild plants).
Examples of substitution practice:
| Native requested |
Non-native often supplied |
Comment |
 |
| Prunus spinosa (Blackthorn) |
Prunus cerasifera
(Cherry Plum) |
Cherry Plum has green twigs in spring and is not thorny. |
|
Prunus avium
(Wild Cherry) |
Domesticated cherry trees |
The domestic cultivars of cherry are cheaply grown on the continent from discards arising from the Romanian jam industry. They are completely different in habit and appearance from our native wild cherry. |
|
Rowan
(Sorbus aucuparia),
Whitebeam
(Sorbus aria) |
Various non native species
and hybrids including
Swedish Whitebeam and horticultural cultivars |
Cultivated varieties dominate the amenity market and are mostly designed for prettifying suburban streets and business parks. |
|
| Crataegus monogyna (Hawthorn) |
Central and Eastern European forms. Possibly different species or subspecies. |
Seed is cheaply collected and commercially grown in large Dutch nurseries. |
|
| Alnus glutinosa (Common Alder) |
Trees of Hungarian native
origin and probably selected strains (that are genetically uniform). Also Alnus viridis (Green Alder), not native to
GB, may be substituted. |
Alder seed from Hungary retails @ £10/kg, whereas seed of British native origin sells for £50/kg. British nurseries could sell British seed and tree for less if buyers insisted on British native stock. Until then, the cycle of cheap imports will continue. One study showed that a non-native tree had substantially (35%) larger cones than a native one. |
|
Betula pendula
(Silver Birch) and Betula pubescens
(Hairy Birch) |
Continental varieties,
sometimes different
species |
Birch is a species shows adaptation to local climate. For example, Scandinavian trees planted in Scotland survive less well than native Scottish ones. There appears to be a range of adaptive variation on a north-south cline within Britain. |
|
| Dogwoods (Cornus), Holly (Ilex aquifolium) |
Horticultural varieties are commonly supplied. |
Appearance, time of flowering and bud burst are very different from our native species and forms. |
|
| Lotus corniculatus (Birds'-foot Trefoil) |
Var. sativus is the fodder variety which commonly "appears" in "wildflower"
seed. |
The fodder variety is much larger than the native forms. Some variation exists within native populations (e.g. Scottish plants flower later than southern England ones). |
|
| Wild flowers |
Anything can be supplied! |
Always order from a reputable native flora specialist who can source identify their stock! And be specific when ordering. |
|
| Pond plants such as water lilies (Nuphar, Nymphaea), Yellow Loosetrife, Purple Loosetrife, Marsh Marigold (Caltha), pondweeds and other native aquatics and wetland species. |
Horticultural varieties predominate among the horticultural trade, including sterile double-flowering forms and non-native species. |
Watch out for potentially invasive exotic species, such as New Zealand Swamp Stonecrop (which can take over and completely dominate in a short time) and Parrot's Feather. Only a few native flora specialists keep records on the origin of their stock. |
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Document date: 16 November 1999 with updates Feb 2007
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Overview